Photocell scoring tool

ABSTRACT

A precision scoring tool is described for cutting through the exposed surface of a photocell or similar structure so as to divide the photosensitive layer into electrically isolated sections. A very thin blade is reciprocated across the surface while being immersed in an abrasive slurry. This action results in an extremely narrow cut which will divide the surface into a pair of sections along a line having a high order of straightness. Means are provided to control the geometry and depth of the cut.

United States Patent [72] Inventor Ulyses Stanford Arwine Burbank, Calif. [21] Appl. No. 708,064 [22] Filed Feb. 26, 1968 [45] Patented Jan. 19, 1971 [73] Assignee Lockheed Aircrafl Corporation Burbank, Calif.

[54] PHOTOCELL SCORING TOOL 7 Claims, 4 Drawing Figs.

[52] US. Cl 125/16, 51/59 [51] Int. Cl 1324b 3/46, B28d 1/06 [50] Field ol'Search 51/59, 165; 125/16, 17; 83/616 [56] References Cited UNITED STATES PATENTS 3,326,071 6/1967 Bushman 83/568X 3,032,026 5/1962 Raabe 51/59X 3,418,759 12/1968 Anderson... 5l/165X 15,380 7/1856 McBird 125/16 3,079,908 3/1963 Hunt 125/17 FORElGN PATENTS 21,605 7/1911 Norway 125/16 Primary Examinerl-1arold D. Whitehead Attorneys-George C. Sullivan and Ralph M. Flygare ABSTRACT: A precision scoring tool is described for cutting through the exposed surface of a photocell or similar structure so as to divide the photosensitive layer into electrically isolated sections. A very thin blade is reciprocated across the surface while being immersed in an abrasive slurry. This action results in an extremely narrow cut which will divide the surface into a pair of sections along a line having a high order of straightness. Means are provided to control the geometry and depth of the cut.

7 la I2 PATENTEUJAN i 9 I97:

H 13.555075 SHEET 1D? 2 INVIZN'I'UR. ULYSSES S. ARWINE P'ATEN'TED' am 9 I97! sum 2 OF 2 v INVENTOR. I UVLYSSVES S. ARWINE- PIIOTOCELL SCORING TOOL BACKGROUND OF THE INVENTION It is frequently desirable to separate a photocell or other photosensitive device into a plurality of electrically isolated sections. Heretofore this has been accomplished by means of chemical etching through masks or by photoetching techniques. A severe shortcoming of these prior techniques is that the etchants make a slot in the surface which is undesirably wider than it is deep. Also, it is very difficult by means of prior techniques to control the angles and dimensions between cuts as well as the straightness of the cut. Still another shortcoming of prior techniques is their excessive cost.

The above-noted shortcomings of prior techniques are overcome by the present invention wherein an extremely thin cutting blade is used which operates in conjunction with an abrasive slurry to provide a very narrow, and precisely oriented, slot in the surface to be divided. The reciprocating motion of the blade draws the imbedded abrasive across the surface to be cut. The size of the slot that maybe cut by the apparatus of the present invention is determined primarily by the width of the cutting blade and the size of the abrasive grains of the slurry. In a practical embodiment, the width of the slot may be held to approximately 0.002 inch with a surface finish of IO microinches r.m.s. The geometry of the cut may be precisely controlled and held to tolerances commensurate with the size of the cut being made. Special orientation mounting fixtures are provided toaccurately position the work below the cutting blade.

The present invention may be used for slicing and dicing semiconductor crystals and for cutting other hard materials such as glass, quartz, ceramics, carbides and sapphire. Furthermore, the method and apparatus of the present invention is substantially less expensive than .prior apparatus and techniques intended to accomplish generally similar results.

It is therefore an object of the invention to provide a novel and improved method for mechanically dividing a photosensitive, surface into electrically isolated sections.

Another object of the invention is to provide a novel and improved scribing tool capable of making rectilinear cuts of very small size to a high order of accuracy.

Yet another object of the invention is to provide a novel and improved scribing tool for use in conjunction with an abrasive slurry in orderto cut elongated slots'in a surface, to a high order of accuracy.

.Still another object of the invention is to provide a novel and improved method for scribing planar surfaces or the like.

These and other objects of the invention will be more readily understood upon studying the following specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the blade and drive portion of a scoring tool constructed in accordance with the invention.

FIG. 2 is a side .elevational view of a portion of the apparatus of FIG. 1.

FIG. 3 is a photomicrograph of a photocell which has been divided into quadrantsby means of the apparatus of the invention.

FIG. 4is .a schematic wiring diagramof the circuit used to indicate electrical isolation of the sections to be separated.

DESCRIPTION OF A PREFERRED EMBODIMENT There is shown in FIG. 1 a representative embodiment of a scoring device constructed'in accordance with the invention. The device is supported on base member 1 which carries guide member2 and part holding jig.3. The photocell 4, or other 'workpiece to be scribed is rigidly mounted on jig 3. Jig 3 rests on base member 1 and is registered in position by. being urged against orthogonalguideibarsfi and 6. Guide. bars 5 and 6 are secured to base member 1. The cutting blade 7 is positioned perpendicular to photocell 4 so:that its cutting edge may move across the upper surface of cell 4. In a typical construction, the blade may comprise a thin steel razor blade. Drive member 8 is slidably mounted to be rectilinearly translated back and forth in the direction of arrow 9. Cam follower 14 is drivingly connected to drive member 8 via plates 28 and 29.

Pin 11 extends outwardly from cam follower 14 (through plate 28) and carries one end of spring 12. The other end of spring 12 is referenced to stationary base member 1 and is secured thereto by fastener 13. This arrangement will cause cam follower 14 to be urged by spring 12 against cam 15.

Cam 15 is secured to shaft 16 for rotation therewith. Shaft 16 is rotated by motor 10. Lateral pressure pins 17 and 18 are secured to drive member 8 and alternately engage the ends of blade 7 during reciprocation of member, 8. The weight of drive member 8 exerts a downwardly directed force on blade 7 through vertical pressure pin 19. Blade 7 is laterally restrained within the slot found between the rearward and forward portions (21 and 22, respectively) of the guide holder. Plate 23 is provided with apertures through which screw fasteners 24, 25 and 26 extend. The portions of the guide holder located on each side of blade 7 prevent lateral displacement of the blade. During the forward power stroke of the blade 7, pressure pin 18 will be urged against one end of blade 7 to apply a cutting stroke thereto. Conversely, during the spring-driven reverse stroke of member 8, pressure will be applied to the blade 7 by the pressure pin 17. Inasmuch as there is some lost motion of blade 7 between pins 17 and 18, buckling of the blade is effectively obviated. That is, the blade has a floating action through a portion of its reciprocation. This arrangement prevents the blade from catching on the surface of the work and thereafter digging into the surface during the power stroke. A light downwardly directed force is applied to the blade by the weight of member 8 via vertical pressure pin 19.

As can be seen at FIG. 2, the lower cutting edge of blade 7 is immersed in abrasive slurry 27 at the upper face of the work (4). The cutting blade 7 is supported on either side by the rear and forward guides (21 and 22, respectively), since this arrangement prevents skew of the blade with respect to the work. The spacing between lateral presure pins 17 and 18 is greater than the length of blade 7 thus. permitting the blade to float" in the slot in the guide holder. This arrangement also prevents blade 7 from bending or breaking in the event that it snags on the work.

The above-described arrangement results in the slurry being gently pressed between the cutting edge of the blade and the hard upper face of the photocell so as to cut a precision groove therein. In a practical construction the groove may have a width which is less than 0.002 inch and a depth which is approximately 0.005 inch. This is at least an order of magnitude more accurate than can be accomplished with conventional photoetching techniques. Supporting jig 3 for photocell 4 is optically flat and parallel to the blade edge over its total length.

In a typical application slurry 27 comprises diamond bort of an appropriate particle size carried in a mineral oil vehicle. In certain applications an abrasive slurry of silicon carbide (600 to 800 grit) in oil has been found to be suitable.

There is shown in FIG. 3, aphotomicrograph of an actual slot cut in a silicon solar cell, by means of the present invention. The slot is indicated at 31 and electrically isolates sections 32 and 33 of the cell. Scale 34 indicates the size of the slot 31. As canbe seen, slot 31 is substantially smaller than the smallest division of scale 34, which divisions are 0.01 inch apart. It is estimated that the groove in FIG. 3 is 0.002 inch wide.

Means are provided forcontinuously indicating the depth of the cut as cutting progresses in order to monitor the scoring process. Apparatus to accomplish this is schematically shown in FIG. 4 and comprises a pair of ohmmeters 3S and 36. Ohmmeter 35 is electrically connected to the edge of the conductive surface of photocell 4 at point 37, via lead 38. Lead 39 is connected to another edge of cell 34 at point 41. Battery 42 (or other suitable power source) is interposed between ohmmeter 35 and lead 45 in order to indicate the electrical resistance between points 37 and 41. Prior to the scribing or scoring process, electrical continuity will exist between points 37 and 41. The interposition of slot 31 between points 37 and 41 will open the circuit path therebetween. In this way it can be determined when the cut has been completed through the conductive surface of photocell 4. In practice it will be found that the resistance between points 37 and 41 measurably increases as the depth of the cut increases. Thus, the progress of the cut maybe continuously observed on the ohmmeter and the process controlled up to the moment that the slot is cut through, at which time the sections of the photocell connected to points 37 and 41 become isolated.

Similarly, ohmmeter 36 is connected to another edge of photocell 4 at point 45 via lead 46. Battery 47 is interposed between ohmmeter 36 and lead 39 to permit a resistance measurement to be made between points 41 and 45. This arrangement will permit the circular photocell 4 to be divided into quadrants. Four leads, 38, 39, 46 and 48, connect to corresponding ones of the four quadrants comprising cell 4 and may be left intact following the completion of the scoring operation to permit wiring of the cell quadrants into their utilization circuits.

While the foregoing description relates to a preferred embodiment of the apparatus and method for its use with respect to dividing a circular solar cell into quadrants, it should be understood that the invention need not be so limited. For example, the device may be used to slice or dice other hard materials and such materials need not be electrically conductive as in the exemplary case.

While the device has been shown and described in a preferred embodiment, it will be understood that various additions, omissions and modifications can be made by those versed in the art without departing from the intended scope of the invention. Thus, it is to be understood that the invention is to be limited only by the scope of the following claims.

lclaim:

l. A tool for scoring the surface of a photocell or like material, comprising:

means for holding said material;

a planar blade having a continuous cutting edge engageable with said material, said blade being generally disposed in a plane normal to said surface; reciprocating drive means slidably supported with respect to said holding means and engageable with said blade; guide means secured to said holding means and in sliding relationship with said blade for confining movement of said blade to said normal plane; power means for imparting a rectilinear unidirectional driving stroke to said drive means in a first direction through a displacement sufiicient to cause said drive means to move said blade;

spring means operatively connected to said drive means for urging said drive means into engagement with said blade in a direction opposite said first direction; and,

means fixed to said drive means and slidably engaging said blade for continuously urging said blade into engagement with surface of said material.

2. A tool for scoring the surface of a photocell or like material, comprising:

means for holding said material;

a planar cutting blade engageable with said material and generally disposed in a plane nonnal to said surface; reciprocating drive means slidably supported with respect to said holding means and engageable with said blade; guide means secured to said holding means and in sliding relationship with said blade for confining movement of said blade to said normal plane; power means for imparting a rectilinear driving stroke to said drive means in a first direction through a displacement sufficient to cause said drive means to move said blade; and, spring means for urging said drive means and said blade in a direction opposite said first direction, said drive means including;

a first pressure pin drivingly engaging one end of said blade in response to said driving stroke; and

a second pressure pin drivingly engaging the end of said blade opposite said one end in response to the urging of said spring means at the completion of said driving stroke, said pins being separated in said normal plane by a distance greater than the distance between said ends of said blade whereby the displacement of said drive means results in a lost motion with respect to the displacement of said blade. I

3. A scoring tool as defined in claim 1 wherein said holding means includes first and second elongate rectangular guide bars orthogonally disposed in a common plane for selectively holding said material in a given one of two orthogonal orientations with respect to said blade.

4. A scoring tool as defined in claim 1 wherein said reciprocating drive means includes:

a cam surface disposed adjacent one end of said drive means; and

an eccentric cam rotatably carried by said power means and in driving engagement with said cam surface for imparting said unidirectional driving stroke thereto.

5. A scoring tool as defined in claim 1 including electrical circuit continuity means connected across said material at two points lying on either side of the line of engagement of said blade with said material, so as to indicate when the scoring of said material has separated it into two isolated parts.

6. A device for scoring a part having a hard-to-cut surface, comprising:

a base for supporting said device;

a first drive member movably mounted on said base and having a cam follower surface thereon;

a rotary cam in engagement with the cam follower surface of said drive member for imparting a unidirectional translatory motion thereto in a first direction;

a motor drivingly connected to said cam for rotation thereof;

spring means connected between said base and said drive member for urging said cam follower surface into engagement with said cam and for imparting a spring bias in opposition to said first direction;

a planar cutting blade;

positioning means for registering said part in parallel relationship with respect to said base and in perpendicular relationship with respect to the plane of said blade;

guide means secured to said base and having an elongate slot therein for slidably supporting said blade;

a second drive member pivotally coupled to said first drive member for reciprocation therewith;

a first pressure pin secured to said second drive means so as to drivingly engage one end of said blade in response to said unidirectional translatory motion in said first direction; and

a second pressure pin secured to said second drive means so as to drivingly engage the end of said blade opposite said one en in response to the urging of said spring means, said pins being separated by a distance greater than the distance between said ends of said blade whereby the translatory displacement of said second drive means results in a lost motion with respect to the displacement of said blade.

7. A device as defined in claim 6 including an abrasive slurry interposed between said blade and said hard-to-cut surface. 

1. A tool for scoring the surface of a photocell or like material, comprising: means for holding said material; a planar blade having a continuous cutting edge engageable with said material, said blade being generally disposed in a plane normal to said surface; reciprocating drive means slidably supported with respect to said holding means and engageable with said blade; guide means secured to said holding means and in sliding relationship with said blade for confining movement of said blade to said normal plane; poweR means for imparting a rectilinear unidirectional driving stroke to said drive means in a first direction through a displacement sufficient to cause said drive means to move said blade; spring means operatively connected to said drive means for urging said drive means into engagement with said blade in a direction opposite said first direction; and, means fixed to said drive means and slidably engaging said blade for continuously urging said blade into engagement with surface of said material.
 2. A tool for scoring the surface of a photocell or like material, comprising: means for holding said material; a planar cutting blade engageable with said material and generally disposed in a plane normal to said surface; reciprocating drive means slidably supported with respect to said holding means and engageable with said blade; guide means secured to said holding means and in sliding relationship with said blade for confining movement of said blade to said normal plane; power means for imparting a rectilinear driving stroke to said drive means in a first direction through a displacement sufficient to cause said drive means to move said blade; and, spring means for urging said drive means and said blade in a direction opposite said first direction, said drive means including; a first pressure pin drivingly engaging one end of said blade in response to said driving stroke; and a second pressure pin drivingly engaging the end of said blade opposite said one end in response to the urging of said spring means at the completion of said driving stroke, said pins being separated in said normal plane by a distance greater than the distance between said ends of said blade whereby the displacement of said drive means results in a lost motion with respect to the displacement of said blade.
 3. A scoring tool as defined in claim 1 wherein said holding means includes first and second elongate rectangular guide bars orthogonally disposed in a common plane for selectively holding said material in a given one of two orthogonal orientations with respect to said blade.
 4. A scoring tool as defined in claim 1 wherein said reciprocating drive means includes: a cam surface disposed adjacent one end of said drive means; and an eccentric cam rotatably carried by said power means and in driving engagement with said cam surface for imparting said unidirectional driving stroke thereto.
 5. A scoring tool as defined in claim 1 including electrical circuit continuity means connected across said material at two points lying on either side of the line of engagement of said blade with said material, so as to indicate when the scoring of said material has separated it into two isolated parts.
 6. A device for scoring a part having a hard-to-cut surface, comprising: a base for supporting said device; a first drive member movably mounted on said base and having a cam follower surface thereon; a rotary cam in engagement with the cam follower surface of said drive member for imparting a unidirectional translatory motion thereto in a first direction; a motor drivingly connected to said cam for rotation thereof; spring means connected between said base and said drive member for urging said cam follower surface into engagement with said cam and for imparting a spring bias in opposition to said first direction; a planar cutting blade; positioning means for registering said part in parallel relationship with respect to said base and in perpendicular relationship with respect to the plane of said blade; guide means secured to said base and having an elongate slot therein for slidably supporting said blade; a second drive member pivotally coupled to said first drive member for reciprocation therewith; a first pressure pin secured to said second drive means so as to drivingly engage one end of said blade in response to said unidirectional translatory motion in said first direction; and A second pressure pin secured to said second drive means so as to drivingly engage the end of said blade opposite said one en in response to the urging of said spring means, said pins being separated by a distance greater than the distance between said ends of said blade whereby the translatory displacement of said second drive means results in a lost motion with respect to the displacement of said blade.
 7. A device as defined in claim 6 including an abrasive slurry interposed between said blade and said hard-to-cut surface. 